1. Field of the Invention
This invention relates to a structure for enabling an attachment part with a mounting bracket to be separated from a part-mounting portion. More specifically, the invention relates to the structure of the mounting bracket.
2. Related Art
A technique, disclosed in the following JP-A-2000-350331 Publication (Pages 2 to 3, FIGS. 1 to 3), is known as a structure for allowing only a mounting bracket to be positively broken when an accidental external force is applied, for example, to an automotive electric connection box, thereby protecting an electric connection box body. Also, a technique, disclosed in JP-A-2004-328953 Publication (Pages 4 to 5, FIGS. 1 to 2), is known as a structure in which a mounting bracket will not be broken by vibration and an impact developing during the travel of a vehicle, and the mounting bracket is broken by a predetermined rupture load only when an electric connector box body is recovered, and as a result the efficiency of the recovering operation and the recyclability are enhanced.
The two techniques are the same in that they have the structure for allowing the mounting bracket to be broken. Breaking notch portions or breaking holes are formed in the mounting brackets of the two techniques. The electric connection box is adapted to be fixed to a base part such as a vehicle panel through the mounting bracket by tightly fastening a bolt, inserted in a round through hole formed in the mounting bracket, relative to a nut threaded on this bolt. The mounting bracket begins to be broken at the notch portion or the hole portion by a rupture load exerted in a direction of the axis of the bolt.
In the structures of the above conventional techniques, when a rupture load (easily-disassembling load) is applied along the axial direction of the bolt in a fixed condition of the mounting bracket, bending stresses concentrate on the notch portion or the hole portion of the mounting bracket, so that the mounting bracket is broken. Therefore, such a structure has the following problems.
Namely, in the case where the rupture load can be applied only in a direction perpendicular to the axial direction of the bolt (here, for example, in a direction from the through hole of the mounting bracket toward an interconnecting portion connected to the electric connection box body), the development and concentration of the above bending stresses will not occur even if the notch portion or the hole portion exists between the through hole and the above interconnection portion of the mounting bracket, and therefore there is a structural problem that the mounting bracket can not be broken, and therefore the electric connection box body can be separated. And besides, there is a problem that the notch portion or the hole portion has such a structure as not to function for a rupture load applied in the above-mentioned direction.
Countermeasures as achieved by changing the disposition of the mounting bracket relative to the electric connection box body or by changing the shape of the base part greatly increase the cost because of such design change, and also affect the disposition relation to the surroundings, and these can not serve as the desirable countermeasures.